Screw-fastening is commonly used to fix components to a casing (for example, see Japanese Registered Utility Model No. 2509235, and Japanese Laid-Open Patent Publications No. 2001-105310 and No. 2005-239049).
In an electronic device in which a circuit board is installed in a metal casing, the circuit board is often screw-fastened to the casing. In such an electronic device, the circuit board and the casing are often subject to temperature load resulting from, for example, heat generated during operation of the electronic components mounted on the circuit board. The circuit board, which is often made of resin or the like, has a coefficient of thermal expansion larger than that of the metal casing. Under the temperature load, an elastic deformation of the circuit board which has a relatively large coefficient of thermal expansion is suppressed by the metal casing which has a relatively small coefficient of thermal expansion. As a result, a distortion (for example, warpage) may occur in the circuit board. Such a distortion may cause damage to, for example, soldered joints between the electronic components and the circuit board.